Air driven turbine



Dec. 19, 1961 A. B. BLACKBURN 3,013,613

AIR DRIVEN TURBINE Filed Aug. 25, 1958 2 Sheets-Sheet 1 wzz 7/Afv 70 a! 4 L ":uu I 6 g I l i .a70 68 INVENTOR.

/ 4/4122 5. B/ackburzz w BY 0. C J H15 ATTORNEY Dec. 19, 1961 A. B. BLACKBURN 3,01

AIR DRIVEN TURBINE Filed Aug. 25, 1958 2 Sheets-Sheet 2 INVENTOR.

4/421 5. filackbufl? BY 1 15 ATTORNEY 3,613,613 AIR DRIVEN TURBINE Alan B. Blackburn, Troy, Ohio, assiguor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Aug. 25, 15 58, Ser. No. 756,894 8 (Claims. (ill. Nib-68) This invention pertains to air driven turbines, and particularly to a variable pitch air driven turbine including governing means for maintaining turbine speed within preselected limits.

Heretofore, it has been proposed to employ governing means in a windmill, or air driven turbine, having centrifugally responsive fiyweights in the form of counterweights which are supported for rotation about an axis in alignment with the longitudinal axis of the adjustable pitch turbine blades. Governing means for an air driven turbine of this type are shown in copending application, Serial No. 420,277, filed April 1, 1954, in the name of Gerald E. Hook et al., and assigned to the assignee of this invention, now Patent No. 2,857,006. The present invention relates to an improved spring-flyweight droop governor of the blade counterweight type wherein the counterweight is not directly connected to the blade. Accordingly, among my objects are the provision of governor means of the spring-flyweight type for a variable pitch turbine including motion amplifying means between the governor fiyweight and the blade; the further provision of governing means of the aforesaid type including force amplifying means between the governor and the blades; the still further provision of an air driven turbine having an auxiliary counterweight for balancing out the blade centrifugal twisting moment; and the still further provision of an improved governor assembly for an air driven turbine having increased governing stability.

The aforementioned and other objects are accomplished in the present invention by connecting the governor counterweight to a spring biased slider through a linkage, and connecting the blade, or blades, to the spring biased slider through a second linkage. Specifically, the governing means of the present invention are of the droop type inasmuch as the governing means maintain-s turbine speed within a preselected range, and thus differs from an iso-chronous governor which maintains turbine speed substantially constant. The air driven turbine of this invention includes a hub which is connected to an output shaft for driving an accessory, such as a generator or a pump. A pair of turbine blades are journalled in the hub for rotation about their longitudinal axes from a substantially flat pitch position to a maximum positive pitch position. Each turbine blade is attached to a stub shaft projecting radially from the hub to which a counterweight is attached. The counterweight is of such a mass and is so oriented as to exactly balance out the blade centrifugal twisting moment during rotation of the turbine. The auxiliary counterweight for balancing out centrifugal twisting moment of each turbine blade has equal masses disposed on each side of the blade axis whereby the bending moment imposed upon each blade by the counterweight is substantially zero.

In addition, each of the stub shafts rotatably supports a governor counterweight, the governor counterweights being connected by links to an axially movable slider. The slider is engaged by one end of a governor spring, coaxial with the horizontal turbine axis, and constitutes a-movable spring seat therefor. Each stub shaft has a crank arm attached thereto which is connected by a link, or pitman, to the slider. The low pitch position of the blades, namely a fiat pitch position, is determined by engagement of the slider with the hub when the governor spring is fully expanded. The high pitch position of the 3,013,613 Patented Dec. 19, 1961 turbine blades is determined by engagement of the governor counterweight with a stop attached to the hub.

During rotation of the turbine, the governor counterweight seeks a pitch position at which the centrifugal force tending to rotate the counterweight about the axis of the turbine blade is in equilibrium with the opposing force of the governor spring. Movement of the governor counterweight eitects movement of the slider, and. the slider in turn effects pitch adjustment of the turbine blades through the pitmans and crank arms. The linkage between the slider and the turbine blades is geometrically designed to amplify the angular movement of the governor counterweight, and also results in a variable mechanical advantage. Thus, whereas in a typical installation the angular movement of the governing counterweight is limited to 50, the turbine blades may move through an angle of 68. Furthermore, as the governor counterweight moves to its maximtun pitch position, the mechanical advantage between the slider and the turbine blades increases.

When the air driven turbine is stationary, that is When it is withdrawn from an air stream, or when there is no air flow, the governor spring moves the slider to the low pitch stop position so that the turbine blades will be at a substantially flat pitch. When the power unit is placed in an air stream, rotation of the hub about its horizontal axis will produce centrifugal force tending to rotate the governor counterweights about their axes. The governor will maintain the speed of the turbine within a range of 5700 r.p.m. to 6600 r.p.m. with a nominal speed setting of 6000 r.p.m. The arrangement of the governor is such that at any of the preselected speeds of turbine rotation within the aforementioned range wherein the blades have a corresponding blade angle position, the opposing forces acting on the blades will be in equilibrium.

Further objects and advantages of the present invention will be apparent from the following description, reference being bad to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a front view, in elevation, of an air driven turbine unit constructed according to the present invention.

FIGURE 2 is an enlarged view, partly in section and partly in elevation, taken along line 22 of FIGURE 1.

FIGURE 3 is an enlarged sectional view taken along line 3-3 of FIGURE 1.

FIGURE 4 is a fragmentary sectional view taken along line 44 of FIGURE 2.

FIGURE 5 is a fragmentary view, partly in section and partly in elevation, taken along line 5-5 of FIGURE 3.

With particular reference to FIGURES 1 through 3, the air driven turbine, or windmill, includes a substantially parabolic spinner 10 which encloses the root portions of a pair of turbine blades 12 extending radially therefrom. As seen in FIGURE 2, each turbine blade 12 has a hollow root portion l4 supported for rotation about its longitudinal axis by ball bearing means 16 in a hub 18. The hub 18 is secured by a plurality of bolts 20 to a'flange 22 integral with a drive spindle, or power output shaft 24. The spinner 10 is suitably secured to a recessed portion of the hub 18 and presents a flush surface with the rear portion of the hub 18 as clearly shown in FIGURE 3.

A turbine hub shaft 26, coaxial with the power shaft 24 is attached to the flange 22 by bolts 29, as shown in FIGURE 2. The hub shaft 26 has a reduced diameter end portion 28 forming an abrupt shoulder 30 as seen in FIGURES 2 and 3. The end portion of the reduced diameter shaft section 28 has a tapped hole 32 therein, and a spring seat 34 is held in fixed relation to the hub shaft by a bolt 36 which threadedly engages the tapped hole.

The spring seat 34 is located coaxially with the axis of the hub 26 by an annulus 38 secured by rivets to the interior of the spinner shell 10.

A cup assembly 40 is secured to the hub 18 by any suitable means, not shown, and engages the shoulder 30 on the hub shaft 26 as seen in FIGURE 3. A coiled compression spring 43 is mounted between the spring seat 34 and a reciprocable slider assembly 42. The reciprocable slider assembly 42 includes a pair of lubricant imprgenated plain bearings 44 and 46 which are held in spaced relation by a bushing 48, the slider assembly 42 being reciprocable relative to the reduced shaft extension 28. A plurality of shims 50 are interposed between the outer end of the governor spring 43 and the spring seat 34, which springs are used to adjust the preload of the governor spring. One or more shims 52 may also be interposed between the end of the slider and the cup assembly 49 for adjusting the mechanical low pitch stop position of the turbine blades 12. A second stop 54 is attached to the flange 22 by bolts 56 for determining the mechanical high pitch stop position of the turbine blades, as will be described more particularly hereinafter. One or more shims 55 may be interposed between the stop 54 and the flange 22 to adjust the high pitch limit.

Referring again to FIGURE 2, the hollow root portion 14 of each turbine blade is rigidly connected by means of a cross-pin 58 to a stub shaft 60 rotatably journalled in a cross-bore of the hub shaft 26 by needle bearings 62. The stub shaft 60 is diametrically opposed and extends radially outwardly from the hub 18. A governor flyweight 64 having substantially equal masses disposed on opposite sides of the axis of the stub shaft is supported for rotation relative to the stub shaft 60 by ball bearing means 66 and 60. An auxiliary counterweight 70 is rigidly attached to each stub shaft 60 by a nut 72.

The function of the auxiliary counterweights 70, which likewise have substantially equal masses disposed on opposite sides of the axis of the stub shaft, is to exactly balance out the centrifugal twisting moment of each propeller blade 12. It is well recognized that turbine blades are subjected to centrifugal twisting moment forces which tend to effect rotation of the turbine blades about their longitudinal axes during propeller rotation. Centrifugal twisting moment forces acting on the blades interfere with governor stability and accordingly in the present invention the effects of the blade centrifugal twisting moment forces are eliminated by the auxiliary counterweights 70.

The governor counterweights 64, as shown in FIGURE 3, have crank pins 74 attached thereto. The inner ends of connecting links 76 are connected to the crank pins 74, and the outer ends of the connecting links 76 are connected by means of pins 78 to the slider assembly 42'. The slider assembly 42 in turn has a pair of pins 80 which are connected to the inner ends of links, or pitmans 82, the outer ends of the links 82 being rotatably connected to crank pins 84. The crank pins 84 are carried by crank arms 86 which are drivingly connected with the stub shaft 60 by keys 88. Since both of the blades 12 are connected by mechanical means to the slider 42, the slider 42 constitutes the coordinating, or synchronizing, mechanism for the two turbine blades and assures that the pitch position of both turbine blades will be the same.

Since it is well recognized that the centrifugal twisting moment forces acting on either a turbine blade or a counterweight, are a sine wave function, that is the centrifugal twisting moment is zero when the center of gravity of the counterweight is either in the plane of rotation or at right angles thereto and is a maximum when the center of gravity of the counterweight is at 45 to the plane of rotation, the angular movement of the governor counterweights 64 is limited in the present governor to an angle A as shown in FIGURE 3, which is susbtantially 50. Moreover, the governor counterweight 64 is so arranged that the centrifugal twisting moment forces produced during movement thereof between its limit positions, do not appreciably vary thereby minimizing the variation in counterweight torque with the blade angle change. Furthermore, the force produced by the governor counterweight is increased by the mechanical advantage of the linkage comprising the links 76 and the crank pins 74. In addition, the range of movement of the turbine blades 12 is throughout the angle B, which may be on the order of 68 as compared to the 50 travel of the governor counterweights. The greater movement of the turbine blades 12 is effected by the geometrical relationship of the pitmans S2 and the crank arms 86 which results in amplifying the movement of the governor counterweight and applying it to the propeller blade. The stability of the governor is greatly increased due to the mechanical advantage of the linkage system, and by reason of the fact that the angular travel of the counterweight is limited to a range wherein the counterweight torque does not vary appreciably. Thus, the aerodynamic twisting moment forces which tend to render the governor unstable are of relatively little significance in the instant governor assembly.

Operation of the improved governor assembly is as follows. When the air driven turbine is withdrawn from an air stream, the governor spring 43 will move the slider 42 to the position of FIGURE 3, wherein the slider engages the shims 52 constituting the low pitch stop position of the turbine blades. This mechanical low pitch stop position may be on the order of a positive 15, and constitutes the flat pitch position of the blades as shown in FIGURES 1 and 2. When the windmill is projected into a moving air stream, rotation will be imparted to the propeller hub 18, and if the air stream is of sullicient velocity the turbine will rotate about its horizontal axis at the nominal governing speed of 6000 rpm. At the nominal governing speed, the centrifugal twisting moment forces acting on the governor counter- Weights 64 will be in equilibrium with the opposing forces of the governor spring 48 and the turbine blades will be at an intermediate pitch position between the low pitch stop position of a positive 15 and a high pitch stop position of a positive 83. Under these conditions, should the load which is driven by the turbine decrease, or the velocity of the air stream increase, the turbine hub will rotate faster thereby increasing the centrifugal twisting moment forces on the governor counterweight 64 which tend to move the counterweight 64 towards the high pitch stop constituted by the abutments 54. This movement of the governor counterweight 64 will move the slider 42 to the left as viewed in FIGURE 3, thereby tending to increase the pitch position of the turbine blades 12 through the links 82 and the crank arms 86. As the pitch position of the turbine blades 12 is increased, the opposing forces will again be in equilibrium with the pitch position of the blades at a higher angle.

Conversely, with the windmill rotating at a nominal speed of 6000 rpm, if the load attached to the power shaft 24 should increase, or the velocity of the air stream decrease, the speed of the turbine will decrease whereupon the force of the governor spring 54 will be greater than the opposing centrifugal twisting moment forces on the governor counterweight 64 so that the slider 42 will be moved to the right whereupon the blades 12 will be moved in the decrease pitch direction through the links 52 and the crank arms 86. When the opposing forces are again in equilibrium, the turbine pitch will remain substantially constant at a lower angle.

While the embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An air driven turbine including, a hub, a blade journalled in said hub for pitch adjustment, a rotatable shaft connected with said hub so as to be driven thereby, a governor counterweight supported for rotation about the axis of said blade, resilient means opcratively engaging said governor counterweight for opposing movement thereof, and a two-way positive driving connection including a movement amplifying linkage operatively interconnecting said counterweight and said blade.

2. An air driven turbine including, a hub, a blade journalled in said hub for pitch adjustment, a rotatable shaft connected with said hub so as to be driven thereby, centrifugally responsive fiyweight means rotatable about the axis of said blade, resilient means operatively associated with said flyweight means for opposing movement thereof, and a two-way positive driving connection including force amplifying linkage means operatively interconnecting said flyweight means and said blade.

3. An air driven turbine including, a hub having a centrally disposed hub shaft, a blade journalled in said hub for pitch adjustment, a governor counterweight supported for rotation about the axis of said blade, a spring mounted coaxially of said hub shaft, a reciprocable slider supported by said hub shaft and constituting a movable spring seat for said governor spring, linkage means connecting said governor counterweight and said slider, and linkage means connecting said slider and said blade for adjusting the pitch position thereof upon rotation of said governor counterweight and constituting a two-way positive driving connection between said blade and said counterweight.

4. The air driven turbine set forth in claim 3 including abutment means attached to said hub and engageable with said slider and constituting a mechanical low pitch stop for said blade, and shim means disposed between said slider and said abutment means for adjusting the mechanical low pitch stop position of said blade.

5. The air driven turbine set forth in claim 3 including abutment means attached to the hub and engageable with said governor counterweight and constituting a mechanical high pitch stop for'said blade, and shim means disposed between said hub and said abutment means for adjusting the high mechanical pitch stop position of said blade.

6. An air driven turbine including, a hub having a centrally disposed hub shaft, a stub shaft rotatably journalled in said hub and extending radially therefrom, a blade rigidly connected to said stub shaft and journalled in said hub for pitch adjustment, a governor counterweight rotatably supported by said stub shaft, a governor spring supported coaxially of said hub shaft, a slider associated for reciprocable movement on said hub shaft and engaging one end of said spring, linkage means connecting said governor counterweight and said spring slider, and linkage means connecting said slider and said stub shaft for adjusting the pitch position of said blade in response to movement of said governor counterweight and constituting a two-way positive driving connection between said blade and said counterweight.

7. The air driven turbine set forth in claim 6 wherein the linkage means interconnecting the governor counterweight and the slider includes a crank pin attached to said counterweight at a point displaced from the axis of rotation thereof and a link interconnecting said crank pin and said slider.

8. The air driven turbine set forth in claim 6 wherein the linkage means connecting said slider and said stub shaft comprises a crank arm rigidly connected to said stub shaft and a linkage interconnecting said slider and said crank arm.

References Cited in the file of this patent UNITED STATES PATENTS Weeks Sept. 17, 1940 

